We, along with our coworkers, have developed significant improvements in the field of industrial heating, home-heating, water-heating and the like units which are comparatively small and efficient and which have significant advantages over metallic structures, especially where heat exchange is carried out to the point that a heat carrier is reduced in temperature below its dewpoint.
The aforementioned copending applications describe the principles involved in the improved burner and heat exchanger assemblies and these principles may be summarized by stating that the heat exchange between two fluids is effected within the ceramic body which can be formed unitarily with thin slit-like passages for the fluids, that the passages for one fluid alternate with passages for the other fluid, and that the ceramic body has walls through which indirect heat exchange between the fluids can be effected.
A suitable heat carrier can be combustion gases which can be used to heat a variety of other fluids, e.g. the combustion air, the fuel or another heat carrier such as water used for central heating or utility water, e.g. to supply the heat and hot-water demands of the residence or other structure.
In turn, any of these fluids can serve as a heat carrier for heating another fluid; for instance the hot combustion gas can be utilized to heat circulating central heating water or fresh water for omestic purposes. In all cases the heat exchange can be effected through walls of any ceramic body so that, for example, if a gas such as the combustion gas contains acidic components, it may nevertheless be cooled below its dew point without engendering corrosion or the like.
The particular class of heating units with which the present invention is most concerned has a burner head supplied with fuel and combustion air and feeding these fluids to a combustion chamber and at least one heat exchanger or recuperator for effecting heat exchange between the combustion gas generated in this chamber and a medium to be heated, both the burner and the heat exchanger having ceramic bodies of the type described, which open toward one another at slit-like passages.
Such burner assemblies can be utilized for large scale generating of heat, e.g. as industrial furnaces or for industrial furnaces as well as for small heat-generating plants, e.g. for space heating in a home or space heating of a room in a home, or for the generation of utility water in the manner described.
The burner head and the recuperator are thus provided in series as described, for example, in the publication entitled Ceramic Components for Thermodynamics and Process Engineering by KFA, Kernforschungsanlage Julich GmbH, Julich, Germany, 1980, and in the aforementioned copending application Ser. No. 253,258. These components are rectangular in cross section and have identical cross sections.